1Division of Epidemiology & Community Health, School of Public Health, University of Minnesota Twin Cities, 1300 South 2nd Street, Minneapolis, MN 55454 USA
2Department of Biostatistics, University of North Carolina at Chapel Hill, 135 Dauer Drive, 3101 McGavran-Greenberg Hall, CB #7420, Chapel Hill, NC 27599 USA
3Department of AIDS/STD Control and Prevention, Guangzhou Center for Disease Control and Prevention, 1 Jiaochang E Rd., Guangzhou Shi, 510000 Guangdong Sheng China
4Division of Epidemiology, The Ohio State University, College of Public Health, 1841 Neal, Ave., 302 Cunz Hall, Columbus, OH 43210 USA
5Division of Infectious Diseases, University of North Carolina at Chapel Hill, 130 Mason Farm Road, 2nd Floor, Chapel Hill, NC 27599 USA
© The Author(s). 2019
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
